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Anismus is thought to cause constipation by producing outlet obstruction during defaecation. It has been described especially in young or middle aged women with chronic constipation 1 2 and may be associated with the inability to defaecate a water-filled rectal balloon. Its main feature is an inappropriate contraction (paradoxical sphincter contraction, PSC) rather than relaxation of the anal sphincter or puborectalis muscle during straining.
Paradoxical sphincter relaxation may be shown by digital rectal examination, manometry, electromyographic examination, and-as a failure of the anorectal angle to widen-on defaecography. As PSC is also found in control subjects without anorectal disease 3 it may be a non-specific finding related to untoward conditions during examination. It seems natural that an embarrassed patient does not show normal defaecation behaviour. Being afraid of losing stools may play an important part in PSC during straining.
The aim of this study was therefore to find out the pathophysiological importance of the anorectal manometric finding "paradoxical sphincter contraction during straining".
Methods
One hundred and two consecutive constipated patients and 102 consecutive patients with stool incontinence were included from our gastroenterological outpatient department. Patients were considered to be constipated if they had had fewer than three bowel movements per week and/or a frequent (>25%) need to strain during defaecation for more than one year and who presented to the hospital because of constipation. Organic disease of the colon had been excluded by colonoscopy, laboratory findings (TSH), and further investigations by the general practitioner. Stool incontinence was defined as an unintentional loss of faeces at least once a week for more than six months.
Eighteen patients referred for colonic surgery or for colonoscopy to exclude colonic malignancy, who were completely free of symptoms, acted as controls.
ANORECTAL MANOMETRY
Anorectal manometry was performed using a seven-lumen side hole catheter (Arndorfer, Greendale, Wisconsin, USA) which was continuously perfused with distilled water at a rate of 0.1 ml/min per recording site (fluid perfusion device, Mui, Mississauga, Canada). There were six side holes, 0.5 cm apart at about 15 cm from the tip of the catheter, radially orientated for examination of the anorectal sphincter muscle, and another side hole was situated 5 cm from the tip of the catheter for determination of the rectal pressure. At the very tip...